Will inter-row sowing work for me

Image of inter-row sowing
Inter-row sowing. Photo: GRDC.

In most farming systems inter‐row sowing will be the preferred option to improve stubble flow and the speed of the sowing operation.

However, on‐row sowing can improve grass weed competition and in non‐wetting soil types may improve crop establishment.

To decide between on-row, near-row and inter-row seeding growers need to carefully consider their soil type, disease inoculum levels, the ability of sowing equipment to precision sow, row spacing and stubble flow and grass weed competition. Table 1 summarises the situations where inter-row or on-row sowing may be suitable.

Table 1. Factors that influence the choice of seeding position. Source: EPARF Sowing position and row spacing in cereal stubbles (PDF 381kb).

 Inter-rowOn-row

Sowing conditions

Ideal sowing conditions with good soil moisture

Dry sowing or drier sowing conditions

Soil type

Soil types other than water repellent

Water repellent soils

Weeds

Low grass weed numbers

High grass weed numbers

Diseases

High stubble-borne disease inoculum levels

Low stubble-borne disease inoculum levels

Nutrition

High soil fertility

Poor soil fertility, nutrition or drought in previous season

Stubble management

High stubble loads with poor trash flow (may be an issue in >2.5t/ha yields depending on grazing levels and sowing system)

Lighter standing stubbles (0.5 to 2.5t/ha yields depending on grazing levels and sowing system at higher yields)

Equipment

Inter-row sowing requires auto steer and implement guidance systems to ensure the repeatable accuracy needed to achieve an accurate sowing position along the length of the paddock. On-row or near-row sowing are also improved by using implement guidance systems.

Inter-row direct drill sowing is more practical with wider row spacing as it can increase trash flow and reduce seeder blockages. However, a yield penalty can occur with wider row spacings. Minimising row spacing with a workable stubble management system is important to maximise grain yield.

With on or near-row sowing there is an increased risk of poor stubble flow and sowing blockages. Another risk is poor seed placement and lower plant establishment, particularly for small seeded crops such as canola. With disc seeders hair‐pinning stubble can reduce seed to soil contact and potentially lower plant establishment.

Stubble-borne diseases

There is more disease inoculum in the on or near-row position compared to the inter-row and this increases the risk for the key stubble-borne diseases: crown rot, take‐all, common root rot, root lesion nematodes and generally Rhizoctonia.

Nutrition

Planting on or near the previous row increases the likelihood that the supply of early-season nitrogen will be reduced. The highest stubble load is found in the previous row resulting in early-season nitrogen immobilisation and lower measured pre-sowing nitrogen in most years.

After a low production season, nutrients are more likely to be available in the old crop row.

Non-wetting sands

On non-wetting sands dry conditions on-row seeding can improve crop establishment. The old stubble row has a wicking effect, increasing soil moisture in the previous crop row.

This was demonstrated at an EPARF trial at Lock in the relatively dry conditions in 2015 (Figure1). These advantages are not evident when sowing into non-wetting soils with good soil moisture or into sands or loams that are not non-wetting.

On-row sowing (left) improved crop establishment over inter-row sowing at Lock in the dry conditions of 2015. Source: EPARF

Figure 1. On-row sowing (left) improved crop establishment compared to inter-row sowing at Lock in the dry conditions of 2015. Source: EPARF Sowing position and row spacing in cereal stubbles (PDF 381kb).

Weeds

Inter-row sowing can increase soil disturbance, meaning that seeds on the soil surface will be incorporated into soils and have a greater chance to germinate.

In EPARF trials at Karoonda, SA, in 2015 brome grass plant and weed seed density were higher following inter‐row sowing compared with on‐row sowing (Table 2).

Table 2. Brome grass plant density (plants/m2) and total seed production (seeds/m2) at Karoonda in 2015. Different letters indicate significantly different data. Source: EPARF Sowing position and row spacing in cereal stubbles (PDF 381kb).

Plant density (plants/m2)Seed density (plants/m2)

On-row

28 b

2022 b

Inter-row

105 a

7332 a

When herbicide options are unavailable, increasing crop competition is one of the most important factors in managing grass weeds such as brome grass.

Interactive tools such as CSIRO’s Brome RIM (BRIM) and Barley Grass RIM evaluate the impact of crop rotations and practices, such as sowing position on weed seed populations.

Legume crops

Legume crops can use the old stubble rows as a trellis and grow higher off the ground, potentially improving harvestability.

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